Class 0

No ossifications.

• Class I

Islands of bone within the periarticular soft tissues.

• Class II

Bone spurs from the pelvis and/or proximal end of the femur (greater trochanter), leaving ≥1 cm between opposing surfaces.

• Class III

Bone spurs from the pelvis and/or proximal end of the femur (greater trochanter), reducing the space between opposing bone surfaces to <1 cm.

• Class IV

Apparent ankylosis of the hip.